Manufacturing method of high-pressure discharge lamp, high-pressure discharge lamp, lamp unit using high-pressure discharge lamp, and image display apparatus using high-pressure discharge lamp

Abstract

A manufacturing method of a high-pressure mercury lamp includes an electric field application step in which an electric field is applied to at least a light emission part ( 4 ) with the high-pressure mercury lamp being kept at a high temperature. This can reduce impurities such as hydrogen and alkali metals in a discharge space ( 8 ) and glass forming the light emission part ( 4 ). As a consequence, blackening and devitrification of the high-pressure mercury lamp while the lamp is lit can be reduced.

1. A high-pressure discharge lamp comprising:
 a glass light emission part forming an enclosed substantially spherical or ellipsoidal opening having a pair of electrodes aligned on a longitudinal axis of the light emission part, each electrode extends from opposite sides of the light emission part along the longitudinal axis into the enclosed opening with a spaced gap between ends of the electrodes, 
 an operative amount of mercury is contained within the enclosed opening to support a discharge; and 
 glass sealed cylinder like parts, connecting the electrodes to the light emission part and extending away from the light emission part, are in alignment with the longitudinal axis wherein the amount of Na per unit volume associated with the glass light emission part around the enclosed opening is smaller than the amount of Na per unit volume in the glass sealed parts connecting the electrodes on the opposite sides of the glass light emission part. 
 
     
     
       2. The high-pressure discharge lamp of  claim 1  wherein the spaced gap between ends of the electrode is within a range of 0.2 mm to 5.0 mm. 
     
     
       3. The high-pressure discharge lamp of  claim 1 , wherein an amount of mercury enclosed in the light emission part is in a range of 0.15 mg/mm 3  to 0.35 mg/mm 3  inclusive. 
     
     
       4. The high-pressure discharge lamp of  claim 1  further including a concave reflector, operatively mounted adjacent the high-pressure lamp in such a manner that a middle point between the electrodes substantially coincides with a focal point of the concave reflector. 
     
     
       5. The high-pressure discharge lamp of  claim 1  further including a collecting unit collecting light emitted from the lamp, an image formation unit forming an image based on light collected by the collecting unit, and a projecting unit projecting the image formed by the image formation unit.